Introduction to WAN Technologies:
?What Is a WAN:
A WAN is a data communications network that covers a relatively broad geographic area and often uses transmission facilities provided by common carriers, such as telephone companies.
WAN technologies function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.
Topics summarized here include:
1- point-to-point links
2- circuit switching
3- packet switching
4- virtual circuits
5- dialup services
6- WAN devices.
Point-to-Point Links:
¢A point-to-point link provides a single, pre-established WAN communications path from the customer premises through a carrier network, such as a telephone company, to a remote network.
A point-to-point link is also known as a leased line because its established path is permanent and fixed for each remote network reached through the carrier facilities.
The carrier company reserves point-to-point links for the private use of the customer.
These links accommodate two types of transmissions:
datagram transmissions which are composed of individually addressed frames.
data-stream transmissions which are composed of a stream of data for which address checking occurs only once.
Circuit Switching:
Circuit switching is a WAN switching method in which a dedicated physical circuit is established, maintained, and terminated through a carrier network for each communication session.
Circuit switching accommodates two types of transmissions:
datagram transmissions
data-stream transmission.
Used extensively in telephone company networks, circuit switching operates much like a normal telephone call.
Integrated Services Digital Network (ISDN) is an example of a circuit-switched WAN technology
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دانلود پاورپوینت فناوری شبکه های گسترده (WAN Technologies)